Korotkoff sounds

As the heart beats, these pulses are transmitted smoothly via laminar (non-turbulent) blood flow throughout the arteries, and no sound is produced.

Eventually, as the pressure in the cuff drops further, the sounds change in quality, then become muted, and finally disappear altogether.

[8] In some patients, sounds may disappear altogether for a short time between Phase II and III, which is referred to as auscultatory gap.

However, there has recently been a move towards the use of the fifth Korotkoff sound (i.e. silence) as the diastolic blood pressure, as this has been felt to be more reproducible.

The time average of the fourth Korotkoff sound represents a reliable pressure marker of diastole of the heart.